This application claims the benefit of Korean Patent Application No. P2002-15967, filed on Mar. 25, 2002, which is hereby incorporated by reference for all purposes as if fully set forth herein.
1. Field of the Invention
The present invention relates to a method of dispensing liquid crystal. More particularly, the present invention relates to a method of dispensing liquid crystal from N liquid crystal dispensing devices onto M panel locations (where M greater than N) such that the amount of liquid crystal dispensed from each of the N liquid crystal dispensing devices over time is substantially the same.
2. Discussion of the Related Art
Portable electric devices, such as mobile phones, personal digital assistants (PDA), and notebook computers, often require thin, lightweight, and efficient flat panel displays. There are various types of flat panel displays, including liquid crystal displays (LCD), plasma display panels (PDP), field emission displays (FED), and vacuum fluorescent displays (VFD). Of these, LCDs have the advantages of being widely available, easy to use, and superior image quality.
The LCD displays information based on the refractive anisotropy of liquid crystal. As shown in FIG. 1, an LCD 1 comprises a lower substrate 5, an upper substrate 3, and a liquid crystal layer 7 that is disposed between the lower substrate 5 and the upper substrate 3. The lower substrate 5 includes an array of driving devices and a plurality of pixels (not shown). The individual driving devices are usually thin film transistors (TFT) located at each pixel. The upper substrate 3 includes color filters for producing color. Furthermore, a pixel electrode and a common electrode are respectively formed on the lower substrate 5 and on the upper substrate 3. Alignment layers are formed on the lower substrate 5 and on the upper substrate 3. The alignment layers are used to uniformly align the liquid crystal layer 7.
The lower substrate 5 and the upper substrate 3 are attached using a sealing material 9. In operation, the liquid crystal molecules are initially oriented by the alignment layers, and then reoriented by the driving device according to video information so as to control the light transmitted through the liquid crystal layer to produce an image.
The fabrication of an LCD device requires the forming of driving devices on the lower substrate 5, the forming of the color filters on the upper substrate 3, and performing a cell process (described subsequently). Those processes will be described with reference to FIG. 2.
Initially, in step S101, a plurality of perpendicularly crossing gate lines and data lines are formed on the lower substrate 5, thereby defining pixel areas between the gate and data lines. A thin film transistor that is connected to a gate line and to a data line is formed in each pixel area. Also, a pixel electrode that is connected to the thin film transistor is formed in each pixel area. This enables driving the liquid crystal layer according to signals applied through the thin film transistor.
In step S104, R (Red), G (Green), and B (Blue) color filter layers (for reproducing color) and a common electrode are formed on the upper substrate 3. Then, in steps S102 and S105, alignment layers are formed on the lower substrate 5 and on the upper substrate 3. The alignment layers are rubbed to induce surface anchoring (establishing a pretilt angle and an alignment direction) for the liquid crystal molecules. Thereafter, in step S103, spacers for maintaining a constant, uniform cell gap is dispersed onto the lower substrate 5.
Then, in steps S106 and S107, a sealing material is applied onto outer portions such that the resulting seal has a liquid crystal injection opening. That opening is used to inject liquid crystal. The upper substrate 3 and the lower substrate 5 are then attached together by compressing the sealing material.
While the foregoing has described forming a single panel area, in practice it is economically beneficial to form a plurality of unit panel areas. To this end, the lower substrate 5 and the upper substrate 3 are large glass substrates that contain a plurality of unit panel areas, each having a driving device array or a color filter array surrounded by sealant having a liquid crystal injection opening. To isolate the individual unit panels, in step S108 the assembled glass substrates are cut into individual unit panels. Thereafter, in step S109 liquid crystal is injected into the individual unit panels by way of liquid crystal injection openings, which are then sealed. Finally, in step S110 the individual unit panels are tested.
As described above, liquid crystal is injected through a liquid crystal injection opening. Injection of the liquid crystal is usually pressure induced. FIG. 3 shows a device for injecting liquid crystal. As shown, a container 12 that contains liquid crystal, and a plurality of individual unit panels 1 are placed in a vacuum chamber 10 such that the individual unit panels 1 are located above the container 12. The vacuum chamber 10 is connected to a vacuum pump that produces a predetermined vacuum. A liquid crystal display panel moving device (not shown) moves the individual unit panels 1 into contact with the liquid crystal 14 such that each injection opening 16 is in the liquid crystal 14.
When the vacuum within the chamber 10 is increased by inflowing nitrogen gas (N2) the liquid crystal 14 is injected into the individual unit panels 1 through the liquid crystal injection openings 16. After the liquid crystal 14 entirely fills the individual unit panels 1, the liquid crystal injection opening 16 of each individual unit panel 1 is sealed by a sealing material.
While generally successful, there are problems with pressure injecting liquid crystal 14. First, the time required for the liquid crystal 14 to inject into the individual unit panels 1 is rather long. Generally, the gap between the driving device array substrate and the color filter substrate is very narrow, on the order of micrometers. Thus, only a very small amount of liquid crystal 14 is injected into per unit time. For example, it takes about 8 hours to inject liquid crystal 14 into an individual 15-inch unit panel 1. This decreases fabrication efficiency.
Second, liquid crystal 14 consumption is excessive. Only a small amount of liquid crystal 14 in the container 12 is actually injected into the individual unit panels 1. Since liquid crystal 14 exposed to air or to certain other gases can be contaminated by chemical reaction the remaining liquid crystal 14 should be discarded. This increases liquid crystal fabrication costs.
Therefore, a method of disposing liquid crystal between substrates using a plurality of liquid crystal dispensing devices would be beneficial. Even more beneficial would be a method of using N liquid crystal dispensing devices to disposing liquid crystal on M substrate locations, wherein M greater than N, such that the amount of liquid crystal dispensed from each of the N liquid crystal dispensing devices over time is substantially the same.
Accordingly, the present invention is directed to provide a method for dispensing liquid crystal that enables increased efficiency and reduced liquid crystal consumption by applying liquid crystal from a plurality of liquid crystal dispensing devices onto a plurality of liquid crystal panels that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Another advantage of the present invention is to provide a method of dispensing liquid crystal from N liquid crystal dispensing devices onto M panel areas, wherein M greater than N, such that each liquid crystal dispensing device applies substantially the same amount of liquid crystal over time. This beneficially reduces refilling, cleaning, and set-up problems associated with refilling liquid crystal into the liquid crystal containers.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for dispensing liquid crystal, wherein liquid crystal is applied onto a substrate on which a plurality of liquid crystal panel columns are disposed using a plurality of liquid crystal dispensing devices. The plurality of liquid crystal dispensing devices apply liquid crystal onto a plurality of liquid crystal panel columns, except onto a first column. A first liquid crystal dispensing device of the plurality of liquid crystal dispensing devices subsequently applies liquid crystal onto the first column. The plurality of liquid crystal dispensing devices then apply liquid crystal onto a plurality of liquid crystal panel columns of a second substrate, except onto a second column. Then, liquid crystal is applied onto the second column using a second liquid crystal dispensing device of the plurality of liquid crystal dispensing devices.
The principles of the present invention further provide for a method of applying liquid crystals from N liquid crystal dispensing devices onto a plurality of substrates, each substrate having a plurality of liquid crystal panels aligned in M columns, wherein M is greater than N. That method includes applying liquid crystals from the N liquid crystal dispensing devices onto the liquid crystal panels in N columns of a first substrate. Then, applying liquid crystals onto the liquid crystal panels of an N+1th column of the first substrate using a first liquid crystal dispensing device of the N liquid crystal dispensing devices. Then, applying liquid crystals from the N liquid crystal dispensing devices onto the liquid crystal panels in N columns of a second substrate. Finally, applying liquid crystals onto the liquid crystal panels of an N+1th column of the second substrate using a second liquid crystal dispensing device of the N liquid crystal dispensing devices.
The principles of the present invention further provide for applying liquid crystals from the N liquid crystal dispensing devices onto the liquid crystal panels in N columns of a third substrate, and then applying liquid crystals onto the liquid crystal panels of an N+1th column of the third substrate using a third liquid crystal dispensing device of the N liquid crystal dispensing devices. Furthermore, the principles of the present invention provide for applying liquid crystals from the N liquid crystal dispensing devices onto the liquid crystal panels in N columns of a fourth substrate, and then applying liquid crystals onto the liquid crystal panels of an N+1th column of the fourth substrate using a fourth liquid crystal dispensing device of the N liquid crystal dispensing devices.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.